controllers behaviour in rrbot

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Dear all,

I need your help to understand how the controllers are implemented and behave in a simple tutorial that I experiment.

I experiment with the a simple rrbot as it is described in the "Tutorial: ROS Control" in http://gazebosim.org/tutorials/?tut=ros_control

So my first question is just a clarification. When I manually send a simple command such as:

rostopic pub -1 /rrbot/joint1_position_controller/command std_msgs/Float64 "data: 1.0"

it moves as expected by rotating the first joint

so I assume that since we move to the desired angle the actuator which is driven by the joint1_position_controller is locked and the rrbot stays there for the rest of the simulation until we send a new command (correct?).

Now comes my question. In order to spawn the joint controllers I use a launch file, as it referred in the tutorial.

roslaunch rrbot_control rrbot_control.launch

This launch file loads and starts the joint position controllers.

When I finish my experiments, I terminate this launch script (ctrl+c), and I can see that the script stops and and unloads the controllers. So it looks like:

[INFO] [WallTime: 1495615574.379552] [56.097000] Started controllers: joint_state_controller, joint1_position_controller, joint2_position_controller
^C[robot_state_publisher-2] killing on exit
[rrbot/controller_spawner-1] killing on exit
[INFO] [WallTime: 1495617523.980943] [1997.811000] Shutting down spawner. Stopping and unloading controllers...
[INFO] [WallTime: 1495617524.984322] [1998.820000] Stopping all controllers...
[INFO] [WallTime: 1495617524.986878] [1998.823000] Unloading all loaded controllers...
[INFO] [WallTime: 1495617524.987001] [1998.823000] Trying to unload joint2_position_controller
[INFO] [WallTime: 1495617524.993683] [1998.830000] Succeeded in unloading joint2_position_controller
[INFO] [WallTime: 1495617524.993904] [1998.830000] Trying to unload joint1_position_controller
[INFO] [WallTime: 1495617525.005732] [1998.837000] Succeeded in unloading joint1_position_controller
[INFO] [WallTime: 1495617525.005949] [1998.837000] Trying to unload joint_state_controller
[INFO] [WallTime: 1495617525.009021] [1998.840000] Succeeded in unloading joint_state_controller
shutting down processing monitor...
... shutting down processing monitor complete
done

The problem is that the rrbot (in gazebo) stays locked. I was expecting whenever we deactivating the controllers the rrbot to unlock and the links to return in their initial position following the gravity.

I tried manually, using the controller_manager, to load - start - stop - unload the controllers but I got the same behavior at the end.

So this is how it has been implemented or I'm doing something incorrect in the procedure?

(ubuntu 14.04, ros indigo, gazebo 2.2.3)

Thanks for your help, Angelos